Easy to view liquid level indication devices that are both accurate and nearly indestructible are known in the art. For example, liquid level indicators sold under the name SURESITE by GEMS Sensors, Inc. of Plainville, Conn. are available for use in applications where quick visual communication of tank contents is required. Such indicators operate without power in temperatures to 750° F. (399° C.) and in pressures up to 4200 psi (290 bar) and are unaffected by extreme thermal changes. In addition, sight glasses are available, although such devices are relatively more fragile and breakable.
Thus, SURESITE liquid level indicators are a durable and safer alternative to sight glasses. Each SURESITE indicator includes an alloy, stainless steel alloy, or engineered plastic housing and mounts externally to a top or side of a liquid storage tank to provide easy-to-read, continuous level gauging. A magnetic level indicator is isolated from the measured media in a pressure-tight housing, allowing the SURESITE indicator to be used in areas where the use of sight glasses may not be possible. The magnetic level indicator comprises a series of vertically-spaced flags each having first sides with a first color and second sides with a contrasting second color. A magnetic float traveling within a housing adjacent to the indicator sequentially flips each flag, thereby showing a series of flags with the first color facing outward a second series of flags with the second color facing outward, thereby indicating that the liquid level is approximately between the first and second series of flags. U.S. Pat. No. 4,512,190 discloses an early fluid level indicator of a similar embodiment. SURESITE indicators are unaffected by tank shape, condensation, atmospheres, foam, stratification of vapors, high temperatures, or flux and do not require continual calibration. Modular accessories, such as switches, scales, and continuous transmitters, increase capabilities.
However, known visual liquid level indicators are difficult to use in dark, tight, confined, or hard to reach locations. For example, known indicators provide far less utility when used in radiator cabinets, engine rooms, or open areas, such as oil storage tank fields, breweries, and dairy farms that use several tanks.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.